Sulfur dye range and processes, and yarns and fabrics produced therefrom

ABSTRACT

The present invention generally relates to sulfur dyeing of fabrics. In particular, a process is provided which provides a sulfur dyed yarn having reduced dye penetration and a white core. The process involves modification of existing sulfur dye ranges in order to more efficiently and in an environmentally improved method produce dyed fabrics. The process involves modifying the immersion time, temperature, pH, and/or dye oxidation of existing sulfur dye ranges. The resulting yarns may then be woven into fabrics used to produce garments.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

This application is related to and claims the priority of U.S. Provisional Patent Application No. 63/154,351, filed Feb. 26, 2021, which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to fabric dyeing, such as fabric dyeing using sulfur dyes. In particular, a process is provided which provides a dyed yarn having reduced dye penetration and a white core. The process involves modification of existing sulfur dye ranges in order to more efficiently and in an environmentally improved method produce dyed fabrics. The invention also is directed to yarns dyed on dye ranges through use of the process, and fabrics formed from the dyed yarns.

BACKGROUND OF THE INVENTION

Like many great discoveries, yarn dyeing with sulfur dyes was realized by accident in the late 1800s, approximately 5,000 years after the discovery of indigo dyes. With indigo dyeing infrastructure in place, the similarities in dyeing technique with the two different chemistries typically occur on ranges that are designed identically or similarly to the range equipment designed for indigo dyes. The appeal of sulfur dyes over indigo dyes (or as dyes that complement indigo dyes) is multifaceted. Indigo dyeing requires the growth of indigo plants, which occupy both land and water resources that can otherwise be used for feed crops. This inefficient process of creating indigo dyes is costly, in addition to the excessive use of resources. Some of the appeals of indigo are the rich blue color but, perhaps more importantly, how that blue color fades. Sulfur dyes are typically utilized when the desired color is a shade of blue that is darker than can be readily made with indigo dyes alone. Other times, sulfur dyes are used to achieve colors that do not involve blue at all. Most commonly, black or grey colors call for the use of sulfur dyes, but other colors are achievable as well.

Sulfur dye is different from indigo dye in many ways; and fading characteristic is one of them. The molecules of indigo are relatively small when compared to the molecules of both the cotton fibers and the molecules of sulfur dyes. How well a dye tends to maintain its bond to the fiber (typically cotton or cotton blend) is generally referred to as fastness. How well a dye has fasted to the yarn determines the amount of energy, water, or chemistry that is necessary to remove the dye from the yarn after oxidation occurs. With the larger molecules of sulfur dyes, sulfur dyes have much stronger bonds with the yarn fibers, meaning the sulfur dyes tend to resist fading from both wash and wear more than indigo dyes.

A dye range is an array of equipment that is used together to dye yarns. There are many stages to a dye range, and each dye range may differ from another. When a design involves a darker shade than is easily achievable with indigo alone but still involves the color blue and intentional fading, two dyeing technologies, indigo dyeing and sulfur dyeing, may be blended. There are several range configurations used for blending indigo and sulfur dyes in the industry:

1. Some dye ranges are equipped with the ability to make sulfur bottom, indigo top. This involves first exposing yarns to a sulfur dye process (immersion and oxidation) and then exposing the yarns to the indigo dye process.

2. Ranges can also be equipped to apply indigo as the bottom dye, and sulfur dye last, referred to as indigo bottom, sulfur top.

3. Ranges are often equipped to apply sulfur dyes alone, without indigo dyes. This is particularly appealing when the goal is a very dark grey or black color. Alternatively, sulfur dyes can be made to be almost any color. Here, the sulfur chemistry is identical, but a different chromophore is used to achieve the different colors. The inventors have multiple patents granted on methods used to achieve improved dyeing results and the inventions are referred to as CleanKore which is not specific to the color, but rather the methods used to achieve the dyeing results.

4. Less common are the dye ranges where the indigo dye and sulfur dye alternate repeatedly in layers. These layers may be, e.g., sulfur indigo, indigo sulfur, or indigo sulfur indigo, demonstrating both unique dye ranges as well as techniques. Particularly following sulfur dye exposure, it is commonplace for yarns to be exposed to air oxidation and then rinsed or washed of dyestuff to reduce contamination in the tanks that follow. In some circumstances, the dye range may even be equipped to have drying stages between dyeing stages with the thought being that dry yarns that are then subsequently immersed in the tank that follows will more quickly pull dye into the yarns.

There may be other dye range variations not disclosed herein.

The result of all these traditional dye range configurations, when paired with sulfur dyes, is the consistent difficulty in removing the dye from the yarn. These dyes are difficult to remove, in part, due to the strong bond between the sulfur and the yarn substrates but, more importantly, because these traditional dye range configurations and practices involving sulfur dye result in excessive dye penetration into the yarn. Excessive dye penetration occurs when the dye penetrates beyond the surface of the yarn to an extent that is beyond the minimum penetration level required to achieve the desired shade. A “desired shade” can be understood to mean a shade deemed appropriate by a user, designer, or operator. The desired shade (or target shade) is particular to a given design or style. Manufacturers have acceptable and unacceptable shade variations from the target shade. While the target shades may vary from one design to another, the realization of dyeing to that specific shade is finite per the specification of the style of fabric.

In a design environment that often favors an appearance of wear, distress, or color loss, sulfur dyeing has a significant disadvantage in that it is substantially more difficult to remove the dyes whether that be using oxidation, laser irradiation, or mechanical abrasion. This in turn results in an inordinate amount of energy used to achieve a particular appearance while using sulfur dyes. Sometimes the dye proves so difficult to remove that sulfur dyeing is avoided altogether.

Therefore, there remains needs for sulfur dye range and methods for producing sulfur dyed yarns which have reduced dye penetration into the yarn resulting in a dyed yarn with a white core at the center of the yarns.

SUMMARY OF THE INVENTION

The present invention provides a solution to the issue of excessive dye penetration of the yarns through the implementation of several embodiments. The inventive processes (also referred to herein as CleanKore) disclosed herein have proven to reduce dye penetration in the sulfur dyeing process. The optimization of dye penetration, as well as the minimization of dye penetration variation for sulfur dyeing processes, results for the first time in yarns that form a fabric that is significantly more receptive to laser abrasion, manual abrasion, and oxidizer treatments used to remove color based on the style specification. The processes disclosed herein increase yarn dye consistency and optimization comes with fewer rejected garments resulting in chargebacks throughout the supply chain.

The present invention identifies, improves upon, and modifies one or more steps in existing conventional sulfur dye ranges to achieve dyeing of the yarn while retaining a white core at the center of the yarn. Referring to FIG. 1, which shows cross-sections of five different dyed yarns at different levels of dye penetration, the peripheral portions of the yarns are dyed (black), and the center of the cross-section remains white (not dyed). The yarns 1.1 and 1.2 are dyed completely, or nearly completely to the core, leaving very little original white core to be revealed. Yarns 1.1 and 1.2, when viewed as a cross-section, may appear to be solid in color, or possibly lighter in color toward the core but still obviously dyed through the core, thus providing an example of a yarn that has significant dye penetration and, to the unassisted eye, still appears quite dark. The core of the yarns 1.1 and 1.2 may be an even lighter color, or possibly even have a few fibers within the center that appear white, but the excessive penetration creates a barrier impenetrable by laser abrasion. Yarn 1.3 is an example of a core that with the unassisted eye may appear to have a white, or significantly lighter shade core, but the dye penetration is still impenetrable by laser abrasion as it extends too far from the perimeter of the yarn. Yarn 1.4 is an example of a yarn that is dyed without consistency as measured from the perimeter of the yarn. This yarn may appear exceptional to the naked eye, displaying a larger area of the yarn that is undyed revealing lighter shades of dye, or even large areas of white in the yarns. These are some of the least desirable yarns, as they result in streaking and inconsistencies after weaving, with uncontrolled portions being dyed vs undyed. Similarly, laser penetration is received as randomly as the dye, leaving patches and undesirable peppering of areas that were intended to have dye removed, but many areas are impenetrable. Yarn 1.5 is an example of the goal of ring dyeing: low yarn penetration while still displaying consistency in dye penetration, with a dark shade on the exterior perimeter of the yarn and a white or nearly white core. This type of yarn readily receives laser energy sufficiently to replace potassium permanganate in the manufacturing process as the chemical bleaching is unnecessary. Yarn 1.5 is most comparable to the yarns dyed with the present invention. Cotton fibers are naturally occurring, with the randomness of the fibers introducing some variables, which, when paired with inconsistencies in twist, etc., result in some variation in dye penetration relative to the perimeter of the yarn, but the results of the inventive technology are to minimize this effect as much as possible. Preferably, implementation of the present invention results in consistent dye penetration about 10% to about 35% of the cross-sectional area of the yarn. Dying the periphery with controlled depth penetration and allowing the core to remain white is advantageous, particularly when the resulting fabric is subjected to laser abrasion, manual abrasion, and/or oxidizer treatments to remove color.

The present invention modifies the scouring stage (or phase), the scour rinsing stage, the dyeing stage, the oxidation stage, and/or the dye rinsing phase of existing dye ranges. The modifications may be applied individually or any combinations thereof to existing dye ranges to reduce and optimize sulfur dye penetration in order to form dyed yarns resembling Yarn 1.5.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated in and constitute a part of the specification. The drawings, together with the general description given above and the detailed description of the exemplary embodiments and methods given below, serve to explain the principles of the invention. The objects and advantages of the invention will become apparent from a study of the following specification when viewed in light of the accompanying drawings, in which like elements are given the same or analogous reference numerals and wherein:

FIG. 1 is a drawing showing cross-sections of five different dyed yarns with different dye penetration levels;

FIG. 2A is a micrograph showing an example of a conventionally dyed sulfur black yarn;

FIG. 2B is a drawing rendition of FIG. 2A;

FIG. 3A micrograph showing an example of a sulfur black yarn dyed using the present invention;

FIG. 3B is a drawing rendition of FIG. 3A;

FIG. 4A is a photograph of a denim garment with the left leg (wearer's right leg) made from conventional sulfur dyed fabric and the right leg (wearer's left leg) made from the CleanKore sulfur dyed fabric;

FIG. 4B is a drawing rendition of FIG. 4A;

FIG. 5 is a diagram showing a dye range;

FIG. 6 is a drawing showing an exemplary vat in the dye range;

FIG. 7 is a drawing showing a yarn being threaded through the vat of FIG. 6 using all of the rollers; and

FIGS. 8.1-8.8 are drawings showing different configurations of a yarn being re-threaded through the vat of FIG. 6 using some of the rollers while skipping others.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of the workflow on a dye range 100 is shown in FIG. 5. Dye ranges include many large containers called vats 102 (or boxes or tanks). These vats 102 are commonly filled with thousands of liters of chemicals, water, and/or dye. The vats 102 serve different purposes and therefore have chemicals that differ from vat to vat. As yarns 106 progress through the dye range 100, they pass over rollers 104 (nip rollers 104 a and regular rollers 104 b are referred herein collectively as rollers 104) that range from a few inches to a couple of feet in diameter. These rollers 104 are found within the vats 102, as well as outside the vats 102. Nip rollers 104 a pull the yarns through the range 100 while also squeezing moisture from the yarns 106; and regular rollers 104 b are simply rollers that the yarns 106 pass over. Nip rollers 104 a will be addressed in greater detail below. The yarns 106 pass over (or under) the various rollers 104 as they progress through the range 100. An exemplary vat 102 and associated rollers 104 a, 104 b are shown in FIG. 6. A plurality of regular rollers are used and are denoted in FIG. 6 with subscript numerals.

The dye range 100 first scours the yarns 106 to wash them of impurities, such as oils and waxes, in scouring vats (tanks or boxes) 102 a. The scouring process (scouring stage) prepares the yarns 106 for dyeing. After scouring, the yarns 106 are washed, typically a vat filled with water that is flowing with fresh water causing contaminated water to overflow to a drain, in a scour rinsing vat 102 d to remove chemicals used in the scour vat 102 a from the yarns 106 (scour rinsing stage). The yarns 106 are then dyed in a plurality of dye vats 102 b (dyeing stage). After each dye vat 102 b, the yarns 106 are exposed to air by passing through a plurality of regular rollers 104 b above the dye vats 102 b to allow the dye to oxidize (oxidation stage). After dyeing, the yarns 106 are passed through rinsing vats 102 c to remove excess dyes on the yarns 106 (dye rinse stage). Once rinsed, the yarns 106 are dried, e.g., such as by using drying cans 108.

The dye range 100 begins with the scouring process. The scouring process traditionally involves one or more scouring tanks or vats 102 a within which yarns 106 are passed over and under a series of rollers 104 a, 104 b. The scouring vats 102 a are filled with water and chemicals, such as caustic soda, chelate agents, and wetting agents, such as Primasol™ from Archroma, for example; and composed of a series of regular rollers 104 b that cause the yarns 106 to be immersed in the chemicals as the yarns 106 move through the range 100.

After having passed through the scour vat(s) 102 a, the yarns 106 are then rinsed in water. We refer to this step as the scour rinsing stage, which occurs in one or more scour rinse vats 102 d. The scour rinse is desirable and removes the caustic and contaminants before the yarns 106 are passed through the dye vats 102 b containing dye chemistries.

Dye vats 102 b are large tanks containing a dye solution (or dye chemistry), within which the yarns 106 pass over a series of rollers 104. The size of the dye vats 102 b is typically over 250 gallons each, with some as large as 700 gallons. The yarn path over or under regular rollers 104 b in dye vat 102 b typically immerses the yarns 106 in the dye chemistry.

After each dye immersion vat 102 b, the yarns 106 are processed through a nip roller 104 a and then enter a dye oxidation stage. It is during the dye oxidation stage that the yarns 106 are exposed to air through a series of regular rollers 104 b. Sulfur and indigo dyes are not water-soluble. During the immersion stage, the dyes are reduced to a soluble state through the removal of oxygen. Once the yarns 106 exit the immersion vats 102 b and begin the exposure to oxygen, the dye returns to an insoluble state, effectively bonding the dye to the yarns 106.

After the last dye cycle of dye immersion and oxidation (with the nip rollers 104 a in between), the yarns 106 proceed to a dye rinse stage, which typically occurs in one or more dye rinse vats 102 c. This dye rinse stage rinses the yarns 106 of excess dye and removes dye that has not fasted to the yarns 106 during the oxidation phase. The number of dye rinse vats 102 c at a given mill on a given range 100 may vary between one to three.

The present invention (also referred to herein as CleanKore) involves modifying conventional dyeing ranges and processes to produce a yarn with a sulfur dyed periphery, while its core remains white. The CleanKore technology also provides significant savings in chemicals, water, and energy compared to conventional sulfur dyeing processes. The modifications include, but are not limited to, changing the scouring stage, limiting sulfur dye immersion, rethreading the yarn path, reducing sky oxidation, expose sulfur dyes to water for oxidation, and/or limiting water rinses (dye rinse stage) after dyeing.

1. CleanKore Scouring Technique

Conventional dyeing techniques with sulfur dye often promote the concept of more dye on the yarns results in richer colors. The metric for determining the amount of dye added to the yarn is the weight. A section of the undyed yarn is weighed. Later, an equal length of yarn is dyed, dried, and then weighed again. The flaw in this determination of color based on weight is that most of the additional steps used to increase the amount of absorbed dye also affect the amount of dye absorbed by the core. Rather than making the yarn darker, a greater area of the cross-section is dyed, making the yarn (unnecessarily) heavier. In one example, a sulfur black dye style was issued as a “control.” This control had a scour (often referred to as prewet) box 102 a immersion time of 22 seconds and scour chemistry consisting of 6 grams per liter of wetting agent and 20 grams per liter of caustic (100% concentration). Wetting agents act as surfactants and are available commercially. One exemplary wetting agent is Primasol NF, distributed by Archroma. These control parameters created excessively alkaline conditions in comparison to the preferred room temperature of the CleanKore scouring techniques. In the CleanKore trial conducted to replicate the shade achieved with the control, modifications were made to the scour vat chemistry. The caustic in the scour vat 102 a was reduced to a mere 4.5 grams per liter (100% concentration) and the wetting agent was reduced to 2 grams per liter. The immersion time was also lowered from the conventional 22 seconds to approximately 9 seconds at room temperature. The CleanKore range for scour immersion time is between 4 and 18 seconds, with a preferred range of 7 seconds to 12 seconds.

Also modified is the minimization of dwell or “sky” time after both the scour box 102 a and the subsequent scour rinse. Air or “sky” time can be understood by those skilled in the art to be the time yarns 106 spend on rollers 104 outside of each respective immersion. These air oxidation times were typically 52 and 22 seconds, respectively. These dwell or sky times were reduced to 5 seconds from the exit of the yarns from the nip roller on the scour tank to the immersion into the scour rinse, because the time the yarns 106 spent in the air only afforded the chemistry on the yarns 106 extended time to impart their effect. In this particular case, the dwell time was reduced to about 5 seconds, but the general CleanKore approach is to significantly lessen or minimize this dwell time, depending on the limitations of each individual range. On a particular range the dwell time may be capable of being reduced to 5 seconds or less. Other dye ranges may require a dwell time that is longer. In the case of scour time, the minimization of this sky time was to better control or limit the amount of time the scour chemistry may dwell or continue to act upon the yarns 106. The caustic chemicals used in the scour process remove the waxes and oils naturally found in cotton yarns, thereby reducing their desirable hydrophobic properties. Wetting agents act as a penetrant, dramatically increasing the efficacy of the caustic, which again works to reduce the hydrophobic properties naturally occurring in cotton yarns. CleanKore technology works through modifications of yarn characteristics, as well as dyeing chemistries, and exposure to chemicals. By employing yarns of a higher twist, in a range of 4.5-5.0 Twist Multiple (TM) and reducing the exposure of the yarns 106 to chemicals that would encourage core penetration, a larger, whiter core is retained with the CleanKore techniques.

Reducing yarn 106 exposure to the scouring chemicals is done through modification of the time the yarns 106 spend in contact with the chemicals in each of the vats by changing the threading or pathing of the yarns associated with scouring, dyeing, and rinsing stages. Also, for the scouring, dyeing, and/or rinsing stages, these methods involve the changing of concentration of the chemicals, the temperature of the process, and, when possible, the expediency and efficacy of the oxidation as described later in this application. Some or all of the chemicals can be eliminated as well. For example, the caustic may be removed from the scour tank 102 a, or the scour process could be entirely skipped, and the yarns 106 could go directly to a rinse tank. When done sufficiently, these larger whiter core yarns make fabric, and consequently garments that are much more environmentally friendly to produce and finish compared to the traditionally made counterparts. Therefore, reducing the exposure of the yarn 106 to scouring chemicals and minimizing dwell time are embodiments of the CleanKore technology. Alternatively, the caustic could be removed from the scouring stage entirely, and the wetting agent, e.g., a wetting agent such as Primasol NF distributed by Archroma, reduced to a mere 0.5 grams to 2.0 grams per liter. In this example, the purpose was to optimize the least amount of wetting agent required while still removing streaks from the dye application on the yarns.

2. Limit Sulfur Dye Immersion

As noted in U.S. Pat. Nos. 10,508,388 and 10,711,397, as well as related pending patent applications, the amount of time spent immersed in the dye chemistry plays a vital role in dye penetration towards the core. Dye ranges are typically set up with dye immersion times of 18-24 seconds per dye vat 102 b at normal operating speeds. Normal operating speed may depend on the specific dye range and may range from 5-32 meters/second. Some ranges may operate from 5-10 m/s, while others from 15 to 25 m/s. Another inventive step is to, however possible, limit the yarn exposure to dye chemistry to a range of 2 to 14 seconds per immersion. Ideally, that range is between 4.0 and 11 seconds. The reduction in sulfur dye immersion is, therefore, an embodiment of the CleanKore technology. These abbreviated immersion times may occur in a single dye tank 102 b, or they may be repeated in multiple dye tanks 102 b in order to achieve the necessary shade. The yarn immersion times may be adjusted due to many variables, but one of the most significant is the range type. Slasher ranges can and typically do expose the yarns to much higher tensions throughout the range compared to rope ranges. With increased yarn tension, the dye is slower to be absorbed into the yarns. In the preferred range, the 6 seconds to 14 seconds is preferred for slasher style ranges with higher tensions, and 3.0 to 12.0 seconds is preferred with the rope style range with the lower yarn tension. Slasher ranges generally involve operators painstakingly dragging individual yarns (thousands of them) through the dye range. Rope ranges involve a multitude of bundles of yarns called ropes. Rope ranges cannot be driven with high tension as the tension reduces the capability of the dye to flow through the fibers of the ropes. Because slashers involve individual yarns, they can operate at higher tension because each yarn is equally exposed to the dye chemistry. The dye ranges typically operation at tensions high enough to get the yarns through effectively, but not so high as to break them (for slasher ranges) or such that the dye cannot penetrate the center of the rope (for rope ranges).

3. Rethread the Yarn Path

The primary method used in adjusting the immersion times and another embodiment of the invention is what the inventors refer to as “rethreading” various parts of the dye range, such as the tanks 102 a, 102 b, 102 c and conventional air oxidation stage as the examples depict in FIGS. 8.1-8.8. Dye ranges are configured such that the yarns conventionally follow a default path involving all rollers across the dye range, as shown in FIG. 7. The Applicants have traveled to dozens of locations in a dozen different countries and have yet to experience a dye range threaded in such a way that could be described as anything other than “normal.” Normal, in this context, means that they follow the maximum length path prescribed by the manufacturer of the dye range, e.g., as depicted in FIG. 7, where all of the rollers 104 are used in threading of the yarns 106. The re-threading of these yarn paths is a novel embodiment necessary in solving the dye penetration problem that arises from excessive immersion times which are conventional. The inventive re-threading process involves skipping some rollers 104 b (which particular to each specified range configuration) to shorten the path and time through stages. The different exemplary ways to rethread the yarns 106 through a vat 102 is depicted in FIGS. 8.1-8.8. FIG. 8.1 re-threads the yarns 106 by skipping rollers 104 b 3 and 104 b 5; FIG. 8.2 skips rollers 104 b 2 and 104 b 5; FIG. 8.3 skips rollers 104 b 2, 104 b 4, and 104 b 5; FIG. 8.4 skips rollers 104 b 3, 104 b 4, and 104 b 5; FIG. 8.5 skips rollers 104 b 4, 104 b 5, and 104 b 6; FIG. 8.6 skips roller 104 b 5; FIG. 8.7 skips rollers 104 b 2 and 104 b 5; and FIG. 8.8 skips rollers 104 b 2 and 104 b 6 (the reference subscripts for the regular rollers 104 b are shown in FIG. 6).

The bypassing of the rollers 104 b affords the opportunity to reduce the time the yarns 106 spend in any particular stage, oftentimes by approximately half, without relying on severe alterations to dye range processing speed. Range processing speed is relative to each range and each desired shade. Where necessary, the speed of the range may be altered to reduce the time spent in dye vat 102 b (and thereby the dye chemistry)]. The preferred method is to thread the yarns 106 in such a way that a bit too much time would be spent in the dye tanks 102 b if run at the conventional maximize productivity, which is yet another embodiment of the invention. Changing the path of the yarns 106 by rethreading the range is an embodiment of the CleanKore process. Although examples of rethreading dye vats are discussed herein, the rethreading of the yarns 106 may be used to reduce the time the yarns 106 spend in any stage of the dye range.

4. Reduce Sky Oxidation

One of the novelties of this invention is in recognizing that the air oxidation stages that follow the dye immersion, although sufficient for indigo dyes, are too slow for sulfur dye. The air oxidation cycle can be too slow to oxidize the sulfur dye quickly enough, such that the sulfur dye only oxidizes on the perimeter of the yarn for the sulfur dyeing process. Conventional threading paths and sulfur dyeing techniques involve exposing the yarns 106 to sulfur dye vats 102 b and then exposing the yarns to air for 50-150 seconds (oxidation stage), and oftentimes repeating these two steps more than once. For example, the yarns 106 processed conventionally with the conditions disclosed prior involved a sky oxidation time of 56 seconds. Rethreading the yarns 106 through the dye tanks 102 b or other tanks does not, by itself, address dye oxidation. To address the issue of dye migration towards the core because of the slow oxidation that occurs with air oxidation of sulfur dye while being “skyed,” the yarns 106 are not skyed at all or are only skyed or oxidized conventionally in the air for much briefer periods, such as 1-30 seconds. Practicing this embodiment, the air oxidation time (or sky time) should be reduced to 30 seconds or less. Ideally this sky oxidation time is minimized, or as close to 0 seconds as possible, where the process still yields acceptable results with limited sky time, such as 1-30 seconds. The elimination or reduction of the air oxidation time significantly reduces the time the dye chemistry may continue to migrate toward the core and is an embodiment of the invention. The time spent in air oxidation is a tunable component with additional rethreading of the yarns 106 on the roller path, depending on the yarn twist, yarn size, desired shade, and chemicals involved in the dye range. Incremental additions to the specified range of time spent in air oxidation will result in incrementally diminished gains in white core retention but reducing or eliminating air oxidation time is an embodiment of the CleanKore process.

5. Expose Sulfur Dye to Water During Oxidation

While sulfur dyes are slow to oxidize in the air, the inventors discovered that they oxidize very quickly when exposed to water (water oxidation). It is for this reason that the necessary and unusually inventive step (water oxidation) is added wherein after each sulfur dye immersion, the yarns 106 are subsequently exposed to a room temperature water rinse vat for a short immersion time of approximately 3-18 seconds, but ideally 5-11 seconds. This short immersion time can take place after a brief air oxidation time, such as 1-30 seconds, or after a minimal dwell time that acts as air oxidation, preferably 30 or fewer seconds between the nip roller 104 a of the dye box 102 b and the oxidation immersion stage. The water oxidation may use tanks added to the process or existing tanks that are removed from the process. In any event, each time the yarns 106 are exposed to sulfur dye, they are subsequently exposed to water oxidation in a vat containing water. The introduction of freshwater oxidation immersion stages is a novel concept. Where traditional sulfur dyeing involves the yarns 106 passing from the dye vat(s) 102 b to air oxidation (repeating several times), the CleanKore process minimizes or eliminates air oxidation. Instead of air oxidation, the yarns 106 are exposed to water oxidation, and only then are optionally exposed to a subsequent sulfur dye immersion, depending on shade requirements. Immersion times in the water oxidation stage can be higher or lower than the time range disclosed above based on the efficacy of the waterflow to the water oxidation boxes to maintain a preferred basic pH of 11.5 or less, but should be exposed to an oxidizing rinse with water after a sulfur dye immersion. The longer the immersion time in the oxidation immersion time over the recommended ranges (3-18 seconds disclosed above) the more important it is that pH of the rinse water needs to be controlled, ideally between a level of 9-10.5 to prevent the oxidizing rinse from becoming so contaminated that the chemistry approaches that from the dye tank, resulting in continued dye penetration of the yarns 106. This control of pH is achieved with the increase of water flow to this water oxidation stage as necessary to maintain the desire pH.

One significant difference between indigo dyes and sulfur dyes is the temperature at which thorough dye reduction to a water-soluble state takes place. With sulfur dyes, the ideal temperature for sulfur reduction in the water oxidation stage is between 65° C. and 100° C. with the most common temperatures witnessed being around 85° C. This temperature requirement for sulfur dye reduction is a profound and beneficial difference in comparison to the indigo dyestuff when the yarns 106 are subsequently exposed to rinse tanks after dyeing. Indigo dyestuffs may be readily reduced to water-soluble form at room temperatures. Applying this water oxidation technique to indigo dyestuffs would result in very light shades due to the reduction in the effective air oxidation indigo dyes experience, in addition to excess dye penetration of the core, since the exposure of water would expose the yarns 106 to reduced (soluble) indigo dyestuffs that would be the product of sustained insufficient water flow to the dye rinse tanks 102 c. This sustained insufficient water flow results in a water vat increasingly polluted with indigo dye reducing chemistry, as well as dye. Water flow is deemed insufficient when the flow rate of freshwater is not high enough to maintain a minimally effective dye-reducing chemistry. These rinses can be measured and determined minimally effective dye reducing chemistry when the pH of said vat is below approximately 10.5 and the mV (oxidation-reduction potential measurement) is −550 or higher (for the sake of clarity, examples of a greater number could be −440, −340, −240, −140, or 0). Increasing the water flow to the rinse tanks could reduce or solve the issue with excessive dye penetration with indigo following this same inventive step, but this would not resolve the significantly lighter shades and wasted indigo. With room temperature water (tap water without additional heating) oxidation, the sulfur dye is too insufficiently reduced to make the increased yarn exposure problematic. Sulfur dye specifically designed to be soluble at lower temperatures is, however, an exception and results in a need for a higher water flow to the water oxidation stage to maintain a pH value of >10.2 and even perhaps shorter exposure or immersion times. Deviations from this specification may result in an improved core compared to conventional sulfur dyeing, but still are not optimal in comparison to the specified parameters of the CleanKore process. Exposure to water oxidation following dye immersion for sulfur dyes is then an embodiment of the CleanKore process.

Also, monitoring and controlling the pH of the sulfur dye is an embodiment of the invention. Conventionally, sulfur dye operates with a pH of 12.6 to 13.2. CleanKore applications work more proficiently at a pH in the sulfur dye tank of less than 12.6, with an ideal pH of 12.0 to 12.5.

6. Limit Rinses Post-Dye

Conventionally sulfur dyed yarns are often rinsed too many times, after the dyeing stages have been completed, resulting in a use of excess water. For example, one set of control dye parameters called for four (4) rinse tanks post dye, each with a 2,000 liter per hour flow rate. For CleanKore technology, one of these rinse tanks was moved to the position after the first dye immersion stage, and a second remained following the second dye immersion stage. Exposing the yarns 106 to a water rinse vat, often referred to as a wash, affords the sulfur dye exposure to water oxidation. The remaining two rinses from the control dye parameters were bypassed during the CleanKore trial. With a dye range processing yarns at 29 meters per minute, 1902 yards of dyed yarns can be expected to be processed by the dye range per hour. With a savings of 6000 liters of water, 3.1 liters of water can be saved for every yard of dyed yarn when utilizing CleanKore technology as opposed to conventionally dyed yarn, in this example. Therefore, an embodiment of the CleanKore technology reduces rinsing after sulfur dyeing stages with the objective of reducing reliance on water for the production of dyed yarns.

When we examine the cross-section of a conventional sulfur black dyed yarn as shown in FIG. 2, the majority of the yarn cross-section is dark gray or black in color. A yarn cross-section dyed in this way would require significant energy to remove the dye from the entirety of the cross-section in order to reveal the original white or near-white color of the yarn, which is a requirement to produce the worn look in denim jeans. This is in stark contrast to the same examination of a sulfur black dyed yarn when the novel and inventive steps outlined throughout this specification are carried out, such as shown in FIG. 3. FIG. 3 reveals a white yarn core with a dark ring of black sulfur dye around the perimeter of the yarn produced with the parameters disclosed for the CleanKore technology. Yarns dyed using the CleanKore techniques outlined throughout this application can be expected to perform similarly while exhibiting excellent dye fastness. However, and most importantly, significantly less energy or chemical is required to remove the perimeter of the dye to reveal partially or wholly the white or near white core of the yarn 106. The average savings across three trials was (per 10,000 meters) 22,572 liters of water, 5704 kWh of energy, and 590.7 kg of chemicals. This is a major benefit of the invention which is not realized with the prior art processing of sulfur dyes.

Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the following illustrative examples, make and utilize the articles of the present invention and practice the claimed methods. It should be understood that the invention is not to be limited to the specific conditions or details described in the examples.

Example 1

Application of the CleanKore technology to a sulfur black trial in Pakistan resulted in significant savings in chemicals, energy, and water compared to sulfur black trials using conventional sulfur dyeing. The comparison of the setups for conventional sulfur dyeing versus the set up for CleanKore sulfur dyeing is shown below, first for the scour and rinse stages and then for the dyeing stages.

I. Scour and Rinse Technique for the Conventional Sulfur Dyed Yarns

In the scour box 102 a, the conventionally dyed yarns were processed with 300 grams per liter of water of 50% concentration of caustic soda and 6 grams per liter of wetting agent per liter of water. This chemistry was added to a scour box that held 3,000 liters of water and chemistry, all of which was heated to 65° C. After this scour box 102 a there were three (3) scour rinse boxes 102 d, each with a 2,000-liter capacity and each was heated to 70° C. with a water flow of 2,500 liters per hour. Each of these scour rinse boxes 102 d, the scour 102 a, as well as the scour rinse boxes 102 d, had the yarns immersed for 22, 20, 20, and 15 seconds respectively.

II. Scour and Rinse Technique for the CleanKore Sulfur Set Up

All the conditions above were then reduced and yielded better dyeing conditions and tremendous water and energy savings, while also significantly reducing the dependence on chemicals. The four boxes 102 a and 102 d were replaced by a scour box 102 a with a chemistry of merely 3 grams per liter of water of caustic at a 50% concentration and 1.5 grams per liter of water of wetting agent and a single rinse, both of which were processed at room temperature (tap water temperature without additional heating or cooling) and for 9 and 7 seconds, respectively. The preferred amount of caustic in the CleanKore scour vat is from 0 g/L to 4 g/L. The preferred immersion time in the scour stage is from 3 seconds to 14 seconds, where 3 seconds to 12 seconds is ideal for a slasher style range with increased tension, and the preferred immersion time in scour on a rope range is from 6 seconds to 14 seconds. This dramatic reduction in scour chemistry, temperature and immersion duration significantly improves the wax retention in the core of the yarn, which in turn favorably reduces dye penetration inwards towards the core. Additionally, the three heated scour rinse boxes 102 d that previously followed the scouring stage were replaced by a single, room-temperature scour rinse box 102 d. This single remaining rinse box 102 d was maintained with a flow rate of approximately 2500 liters per hour, but this flow rate, instead of being fixed, was adjusted to maintain a pH of the scour rinse box of <10.5. The monitoring of scour rinse boxes 102 d for pH levels is a novel CleanKore embodiment. This concept is a unique approach to lessening the impact of the caustic and wetting agents on the yarn center's original waxy makeup. The reduced time in the rinse tanks also plays a role as well.

III. Dye Box Set Up for the Conventional Sulfur Dyed Yarns

After processing the yarns through the scour and scour rinse stages, the conventionally dyed yarns skipped the next eight (8) dye vats] and were then subjected to two successive dye boxes 102 b. The eight skipped dye boxes were part of the existing dye range, which was used for both indigo dye, which was typically associated with a larger number of tanks, and sulfur dye. While any two boxes could be used on the dye range, it was preferred that the boxes at the beginning of the range were skipped, such that the time, from when the yarns 106 left the last dye box to the time it reached the rinse tanks that follow, was minimal. While it is true that most any tank could also serve as a rinse tank as well, quite often the size or water flow capabilities were ideal in actual rinse tanks so they are often preferred, when possible These dye boxes 102 b were maintained at 90° C. temperatures and vat concentrations of 100-300 grams per liter of pre-reduced sulfur dye, 25 grams per liter of a reducer, 5 grams per liter of a wetting agent, plus 90 grams per liter of 50% concentration of caustic, within which the yarns would be exposed to 22 seconds of immersion, per box. The temperature, immersion duration, and chemistry, in line with conventional dyeing with sulfur, generated substantial core penetration of dye, resulting in significant add-on weight of yarns, but at the expense of a dark, heavily dyed core. This would in turn require excessive energy in the dyeing process, as well as both the wet and dry processes to remove some of the dye to generate the worn look in jeans.

IV. Dye Box Setup for the CleanKore Sulfur Dyed Yarns

The CleanKore approach and specifications for dyeing were unique. First, the dye box 102 b temperature was lowered from 90° C. to about 75°-85° C. to lessen the amount of expansion of the yarn 106 due to the temperature (expansion of the yarn invites deeper penetration of the dye into the yarn).

Second, the yarns 106 were threaded through the dye box 102 b in such a way that, along with a modest increase in speed (from 25 meters per minute to 27-30 meters per minute, for example), the immersion time was cut from 22 seconds to a 2 seconds to 13 seconds. These shorter immersion times can be achieved through a variety of choices. One such choice is shown in FIG. 8.1, where a simple V-shaped threading path through the dye tank 102 b is used. This threading path can result in a variety of immersion times based on the specifications of the dye box 102 b, as dye boxes are unique in depth and length from range to range. Where the dye boxes 102 b are too deep and/or too long, an alternative may be a threading path, such as the one depicted in FIG. 8.4, which results in a shallow immersion, typically providing a minimal immersion time. When dye tanks 102 b on a dye range fail to offer a solution with a preferred immersion time, because of roller design and/or box dimensions, the yarns 106 can alternatively be threaded through a box designated for a different purpose, such as a rinse tank. The rethreading, however, may be used with any tank in the dye range. The tank chosen to serve as a dye tank simply requires a source of heating the sulfur dye solution, as well as a supply from chemical feed tanks, also referred to as “the kitchen.” This inventive step reduces the time that the yarns 106 are exposed to dye, as well as the caustic and other reducing chemistries, for example, sodium sulfide (a sulfur dye reducing agent) within the dyestuff, which all affect dye penetration.

Next, the dye feed to the dye tank 102 b was increased from 220 grams of dye per liter to 250 grams per liter to safely offset the reduction in immersion time while still achieving the target shade. Then, in the dye tanks 102 b, the reducer was reduced to 10 grams per liter of water (from 350 grams per liter); the wetting agent was eliminated; and the 50% concentration caustic was reduced from 40 grams per liter to a mere 2.5 grams per liter. Additionally, the pH of the dye tank 102 b was controlled by the amount of caustic in the tank to a range of 11.7 to 13.1. The caustic is used in the dye tank 102 b to achieve a near oxygen free environment to make the dyes water soluble.

Next, following the CleanKore inventive method of water rinse/oxidation of the sulfur dye, the yarn 106 s passed from dye immersion, through the respective nip rollers 104 b, and then, as quickly as possible, exposed to a water bath bypassing the air oxidation stage to the extent possible (some ranges, because of their roller configuration, require at least some air oxidation) in order to immerse the dye and yarns into a water vat to serve as an oxidation bath and rinse at room temperature (tap water temperature with no additional heat added) for approximately 3-12 seconds, but preferably 5-10 seconds. Less time in the water rinse/oxidation stage would result in a drop in oxidation thoroughness and decrease efficacy of loose dye removal. Additional time in the water rinse/oxidation stage would increase the time the yarns spend in water, but also increases the dye pollution rate of the water. As in the case of the scouring rinse box, the water flow rate in the water rinse/oxidation box is, according to the CleanKore technology, monitored to maintain a pH of <10.5. This often requires a water flow of at least twice the capacity of the tank being used, which is an embodiment. For example, if a water rinse/oxidation tank is 800 liters, a freshwater flow rate of 1600 liters per hour may be used to maintain a pH of <10.5. Variables on the dye range impact the contamination rate of the tank and consequently the rinse tank flow rate can be adjusted accordingly. Some examples of these variables could be range speed (higher speed results in more yarn passing through the vat in a given amount of time, requiring higher flow) and yarn diameter (larger diameter yarn carries more chemistry from preceding tanks, lower diameter yarn carries less chemistry from preceding tanks). This flow rate can be adjusted according to the pH, often resulting in even more water savings when compared to using a greater number of tanks, even when the flow rates to individual conventional boxes may be lower. CleanKore uses fewer tanks with the disclosed flow rate often results in a water savings.

Following this water rinse/oxidation stage, the next 6 dye vats were bypassed before the yarns 106 passed through a second and final dye immersion with identical parameters as the first. These were the conditions for this trial, but the dye and then subsequent water rinse/oxidation could be in any of the available dye boxes, so long as the dye immersion stage was similarly followed by a dye freshwater rinse stage at room temperature.

V. Post Dye Rinsing of the Conventionally Sulfur Dyed Yarns

After passing through the dye immersion stages, the conventionally dyed yarn passed through three (3) 2,000-liter dye rinse stages with an average immersion time of 21 seconds with a flow rate of 3000 liters per hour each, heated to 70° C., 70° C., and 50° C. respectively, resulting in tremendous energy consumption. Sulfur dye achieves increased solubility with temperatures above 70°. So, in addition to wasted energy, these higher immersion times and temperatures increase the likelihood of dye migration towards the core of the yarns 106, as these temperatures approach the temperatures required for dyeing conditions with sulfur dyes.

VI. Post Dye Rinsing of the CleanKore Sulfur Dyed Yarn

Conversely, the CleanKore technology used with sulfur black dye required two room temperature water rinse/oxidation vats. These were conducted in two 2,000-liter tanks, with the flow rate in the first tank maintained at 3,000 liter per hour and the flow rate in the second tank reduced to 2400 liters per hour. The yarns 106 were immersed in the dye rinse tanks 102 c for 7 and 11 seconds, respectively. The staggered rinse times, developed through the novel rethreading of the yarns 106 on the dye range 100, served a strategic purpose. The shorter duration of the first dye rinse tank 102 c served to reduce the contamination level within that tank, making the replenishment of freshwater much more effective and maintaining a relatively clean oxygen-rich water in which the sulfur dye can be quickly oxidized (here dye rinse and oxidation occurred in the same tank (water rinse/oxidation process)). Reduction in the contamination level of all water rinse/oxidation tanks is an important element of the CleanKore technology. The monitoring of dye rinse boxes 102 c for pH levels (pH<10.5) is a novel CleanKore embodiment.

Having been quickly oxidized in the first water rinse/oxidation tank 102 c, the yarns 106 are then processed through a longer duration dye rinse cycle from approximately 11 seconds to 18 seconds for the yarns 106 to experience increased strain (the strain yarns experience as passed over rollers 104 a, 104 b) through the roller path, as well as exposure to the water to further remove loose dyes not removed from the first dye rinse vat 102 c. The process of the yarns 106 passing over rollers 104 a, 104 b serves to wring dye from the yarns 106. This is selectively used to rid the yarns 106 of some of the dye in the first dye rinse tank 102 c without the over contamination that can result from a longer rinse immersion in this stage. After the easiest to remove portions of the dye have been removed in the shorter rinse of the first dye rinse tank 102 c, a longer, more strained exposure over more rollers 104 a, 104 b helped to remove even more dye in the second dye rinse tank 102 c. This reduces the loose dye contamination in later fabric finishing, as well as garment manufacturing. In some cases, one rinse tank 102 c may suffice or a shorter immersion time, such as 4-10 seconds, can be used in the second dye rinse tank 102 c.

The CleanKore techniques disclosed in II, IV, and VI above represent exemplary embodiments of the invention.

With the adoption of the CleanKore technology for sulfur dyeing, the disclosed experiment resulted in more efficient rinsing and dyeing of yarns, which in turn generated savings of 5,600 liters of water per hour for this product through the elimination of 2 scour rinse tanks 102 d and the reduced inflow of the second dye rinse tank 102 c. These water savings were achieved, while dramatically improving the dyeing conditions and dyeing results of the yarns. With the CleanKore technology, the dyeing result is expected to produce wet and dry processing at reduced energies due to the reduction in sulfur dye penetration into the core for the yarns.

Yet another inventive step practiced during this trial was an increase in nip pressures of the nip rollers 104 a. Nip rollers 104 a are placed at the exit of each immersion stage for scouring boxes 102 a, scour rinse boxes 102 d, dye boxes 102 b, and dye rinse boxes 102 c. These nip rollers 104 a are responsible for squeezing the chemistry from the yarns 106 and redepositing them into the vat from which the yarns just emerged. Increasing the nip pressure improves the efficacy of this wringing action to reduce the amount of chemistry carried on the yarns into the subsequent stages. The conventionally dyed yarns had nip pressures of 60 PSI throughout their range. CleanKore selectively increases the nip pressures following the immersions that have the greatest impact on dye penetration. For example, the nip pressures on the scouring box 102 a nip roller 104 a were increased to 85 PSI or maximum pressure allowable on a given range to further eliminate caustic from the yarn 106, reducing the time the caustic acts on the yarn 106, as well as reducing the contamination into the scour rinse tank 102 d. Likewise, the dye immersion and dye rinse stages also had their nip pressures increased in a similar fashion to lessen the duration that the chemistries imparted their chemical impact on the yarn 106. The increase in nip pressures is another embodiment.

These inventive processes can be implemented with sulfur bottom, sulfur top, as well as sulfur only dyeing applications. The novel CleanKore approach to the sulfur black dyeing of yarns begins with a thorough examination of each stage on the dye range 100. This examination involves asking “why?” for each of the conventional practices in dyeing. Why is caustic used in the scour box? The answer is, to remove impurities from the yarn to allow dyestuffs to mix with the yarn fibers where the dye will later oxidize, changing the color of the yarn fibers. The next question asked is, “how much caustic is needed?” Conventional dyeing throughout the world, without exception, has exceeded the specifications in CleanKore dyeing. The CleanKore parameters ware determined through rigorous testing, retesting, and analysis of yarn dyeing techniques. The heating of the scour tanks certainly increases the efficacy of the caustic in ridding the yarns of impurities, but the Applicants realized that this was counterproductive to retaining a white core with a thin circumferential ring of appropriate dark dyed yarns. This same lengthy approach has been applied to the dye stages, the nip rollers 104 a between the stages, the scour rinse stage, the water purity in the water rinse/oxidation tanks, as well as the chemistries and even distributors of chemicals and their variations in the quality of chemical products. The CleanKore technology involves methods that take centuries-old dye technology and significantly improve the process with major advancements in the technology for dyeing denim. A dye range 100 can be installed nearly anywhere in the world at an expense in excess of one million USD ($1,000.000.00 USD) and carries with it no more improvements in yarn core preservation than what was experienced previously. It is through the manipulation of these dye ranges and chemistries as, for example, is itemized throughout this application that results in modern and novel dye results that have been unprecedented.

One embodiment of this invention is the application of sulfur black dye in the scouring tank 102 a. It is common that a light (1%-4%) application of sulfur dye is applied in the scour tank 102 a, which is referred to as sulfur bottom, where the yarns 106 would subsequently be exposed to indigo dyes. The purpose of the sulfur application in a sulfur bottom scenario is to have a darker version of indigo dye with a low (1%-4%) add on of sulfur dye. This results in indigo dye being applied on a grayish yarn rather than a white yarn, which aids in creating a darker blue appearance. Rather than a sulfur bottom application, however, this novel approach of dyeing yarns black (not sulfur bottom indigo top) with increased concentrations of sulfur dye than conventionally used within this tank that the yarns are scoured that result in an increased addon, such as 5%-25%. This is referred to as sulfur-scour combination dyeing. In this embodiment, the yarns 106 enter the sulfur-scour combination dyeing dry. In the typical process of sulfur only dyeing, the sulfur is applied to wet yarns. The dyeing process within the sulfur-scour combination dyeing follows the guidelines for both CleanKore scouring, as well as CleanKore dyeing, with reduced immersion times as previously disclosed, as well as the dramatic reduction in chemicals usage. The reduced immersion times and reduced wetting agent and caustic chemistries taught throughout this application also play a pivotal role in the retention of the white core in the sulfur-scour combination dyeing. This CleanKore dyeing practice is generally accomplished in the first tank on the range with a temperature range of 70° C.-80° C. and followed by 1 to 2 rinses to serve both as a loose dye and chemistry removal, as well as water oxidation, as previously described. The yarns 106 then proceed to the end of the dye range 100, bypassing each of the tanks associated with dyeing and dye rinsing, to the extent possible on any given dye range 100 (the scour and dyeing process is combined). Successful experiments have been conducted practicing this method with a mere 1 gram per liter of wetting agent. The dye chemistry was supplemented with 3-7 grams per liter of caustic for a 5%-20% shade (the amount of dye on the yarn) which resulted in excellent white core retention in the yarn. Alternatively, these yarns could also be transferred from a dye rinse/oxidation process to additional sulfur dye immersions before a final water rinse/oxidation in order to achieve shades darker than can be achieved in the single scour/dye vat.

When practicing the lower spectrum of CleanKore dye immersion times, such as 2-6 seconds, other changes may be required when using a sulfur-scour combination tank. While the significantly reduced time in the dye chemistry is beneficial in limiting the penetration of dye toward the core, it also reduces the time the wetting agent has to act on the yarn perimeter. In practicing both of these inventive steps of using the scour tank 102 a as a sulfur black application, as well as significantly reduced immersion times, the wetting agent concentration may need to be increased by 1 g/L to 1.5 g/L, depending on the yarn twist, yarn diameter, yarn tension, and yarn specific hydrophobic properties in order to reduce or eliminate any “streaking” of dye application.

The CleanKore approach to sulfur dye application requires treating each dye range and production goal with a shade and penetration potential. Factors that are determined by the range, such as rope vs slasher, nip pressures availability, and immersion times are all used to determine other factors, such as temperature and chemical concentration, specifically chemicals such as dye, wetting agents, and caustic. For instance, if a single source of cotton were used for a rope range and the appropriate wetting agent concentration were 0.8 gram per liter, the same sourced cotton on a slasher range may require 2 grams per liter to counter with the reduced penetration of chemicals associated with the increased yarn tension on the slasher range, which can be determined by the presence or lack of streaking in the dyed and undyed portions of the yarns. The CleanKore method involves using the least amount of wetting agent as possible while still avoiding streaking.

Another embodiment of this invention is the tuning of the caustic according to pH. Dye ranges all over the world consist of machinery that is polluted with chemistry to varying extents and even the water being used varies in the pH levels. For this embodiment, caustic is added to maintain a pH of 11.2-12.2 within the scour box 102 a, with a preferred range of 11.6-12.0. Maintaining this range helps control the pH in the scour rinse tank 102 d. Excess chemistry in any given stage increases the chance of contamination in subsequent stages. The means to maintaining this pH goal can be varied, but a couple of examples are as follows:

In a first example, the scour tank 102 a may be filled with water from a source which would normally introduce caustic, to take the contamination of all equipment into consideration. This water could be sampled and taken to a lab to be measured for pH levels. Caustic could be added incrementally until the pH reaches the desired goal, within the range of 11.2 to 12.2. Once the operator determines the concentration of caustic necessary to reach the desired target, the caustic dosage can be determined as necessary to maintain the pH from the mixing tanks to the actual scour box. Typically, with newer equipment the caustic dosage is determined by the machine based on the target pH. The equipment typically has a feed of caustic with a valve that opens to feed caustic into the tank as necessary to maintain the target pH.

In a second example, the scour chemistry could simply be mixed with a very light dosage of caustic, such as 0.5 gram per liter to 3.0 grams per liter, and then incrementally raised until the pH reaches the target range. The maintenance of this pH range and methods to do so are embodiments of the CleanKore technology.

Why is CleanKore technology so important? For decades, consumers of denim garments have reveled in the customization of garments through the implementation of washing and abrasion technologies. Washing and abrasion technologies are used to reveal varying degrees of contrast between the dyed cast (the background color) of the garment and the original color of the yarn, as it was before receiving dye. Acid wash, stone wash, laser abraded, hand sand, sandblasted and laser-pattern jeans are all types of garments that consist of combinations of dark, dyed colors and varying levels of lighter shades that resemble white or lighter shades throughout the garment. For decades, these garments have been made conventionally resulting in extraordinary measures being necessary to reveal these lighter colors. These measures utilize staggering amounts of freshwater, require the application of hazardous chemicals, such as potassium permanganate and sodium hypochlorite, electricity, millions of hours of manual labor resulting in countless repetitive injuries, all in attempts to reveal both a dark and light color within garments. With CleanKore technology, the ring dye perimeter is substantially smaller and consistent, meaning less of the yarn cross-section is dyed. As this is the case, the energy, chemicals, and labor required to reveal the contrasting colors within a garment are substantially reduced and in the case of potassium permanganate, typically eliminated. And this is true for both indigo dyeing and sulfur dyeing. When comparing FIG. 2 with FIG. 3, it is easy for one skilled in the art to understand how significant the CleanKore achievement is. When a garment finisher launders, laser abrades, or hand sands a garment in an attempt to reveal lighter, whiter colors beneath the dyed perimeter, a narrower perimeter with a brighter, whiter core is a profound invention. CleanKore dyeing technology, as disclosed herein, has shown repeatedly and consistently to reduce dependence on water, energy, and chemicals in the production of yarns and increased production in the washing and dry processing of denim garments. This reduced dependence on natural resources makes for a more environmentally friendly solution with reduced costs at the mill, at the garment laundry, and eventually for the brands which sell garments constructed with CleanKore technology. An example of such a garment is shown in FIG. 4, which shows a garment constructed with a conventionally dyed sulfur fabric on the left leg after it had been laser abraded and then washed. The same garment is constructed with CleanKore fabric on the right leg of the garment. It is apparent that the significantly reduced dye penetration that is the product of the CleanKore sulfur dyeing technology, such that, when the same energies are applied to the two vastly different processes, the results are remarkably contrasted. The CleanKore technology results in tremendous savings of water, chemicals, energy consumption, reduced repetitive injuries, and reduction or elimination in the usage of harmful chemicals such as potassium permanganate. Further this novel CleanKore will make washing so much more efficient than the productivity at the laundry will improve.

Although certain presently preferred embodiments of the invention have been specifically described herein, it will be apparent to those skilled in the art to which the invention pertains that variations and modifications of the various embodiments shown and described herein may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention be limited only to the extent required by the appended claims and the applicable rules of law. 

What is claimed is:
 1. A method for dyeing a yarn with a sulfur dye, comprising the steps of a. providing a dye range comprising a scouring stage, a scour rinsing stage, at least a first sulfur dyeing stage, and a dye rinsing stage; and b. modifying the operation of the dye range by at least one of the following steps to provide a modified dye range: i. performing the scouring stage in a single scour vat, ii. reducing immersion time in the scouring stage to between 4 seconds and 18 seconds, iii. reducing a wetting agent in the scouring stage to about 0.7 g/L to about 4 g/L, and iv. adjusting immersion time of the yarn in a sulfur dyeing stage to about 3 seconds to 14 seconds.
 2. The method of claim 1, wherein step iv is about 3 seconds to 12 seconds on a rope style dye range.
 3. The method of claim 1, wherein step iv is about 6 seconds to 14 seconds on a slasher style dye range.
 4. The method of claim 1, wherein the sulfur dying stage occurs in a sulfur dye vat containing the sulfur dye maintained at a pH between about 11.7 and 13.1.
 5. The method of claim 1, wherein the scouring stage contains no caustic.
 6. The method of claim 1, wherein the scouring stage involves the use of a wetting agent at between about 0.5 g/L and 2.0 g/L.
 7. The method of claim 1, wherein minimal exposure to air is maintained when the yarn traverses from the dyeing stage to the dye rinsing stage.
 8. The method of claim 1, wherein step ii is accomplished by rethreading the yarn through the range.
 9. A method for dyeing a yarn with a sulfur dye, comprising steps of a. providing a dye range comprising a scouring stage, a scour rinsing stage, an air oxidation stage, at least a first sulfur dyeing stage, and a dye rinsing stage; and b. modifying the dye range by at least one of the following steps to provide a modified dye range: i. adding sulfur dye to the scouring stage, ii. reducing immersion time in the scour stage having the sulfur dye therein to about 3 to 14 seconds, iii. exposing the yarn to no more than 25 seconds to air in the air oxidation stage, and iv. immersing the yarns in a water vat after the dyeing stage so that the water oxidizes the sulfur dye and washes away loose dye.
 10. The method of claim 9, wherein step ii is about 3 seconds to 12 seconds on a rope style dye range.
 11. The method of claim 9, wherein step ii is about 6 seconds to 14 seconds on a slasher style dye range
 12. The method of claim 9, wherein the scour rinsing stage occurs in two scour rinse vats.
 13. The method of claim 9, wherein the yarn is rethreaded throughout the range.
 14. The method of claim 9, wherein the air oxidation stage lasts no more than 25 seconds.
 15. The method of claim 9, wherein the dye rinsing stage occurs in two dye rinse vats containing water.
 16. A method for dyeing a yarn with a sulfur dye, comprising steps of a. providing a dye range, said dye range includes a scouring stage, a scour rinsing stage, a dyeing stage, an oxidation stage, and a dye rinsing stage; and b. modifying the dye range by at least one of the following steps to provide a modified dye range: i. adding sulfur dye to the scouring stage, ii. reducing the air oxidation stage to no more than 25 seconds, and iii. immersing the yarns in a water vat after the dyeing stage so that the water oxidizes the sulfur dye and washes away loose dye.
 17. The method of claim 16, wherein the modifying step further comprises reducing the dyeing stage to about 6 seconds to 14 seconds, when the range is a slasher style dye range.
 18. The method of claim 16, wherein the modifying step further comprises reducing the dyeing stage to about of 3 seconds to 12 seconds when the range is a rope style dye range.
 19. The method of claim 16, wherein the dye rinsing stage occurs in two dye rinse vats containing water.
 20. The method of claim 19, wherein the pH of the dye rinse vats is controlled with freshwater flow rates so that the pH does not exceed 11.5.
 21. The method of claim 19, wherein the modifying step further comprises reducing a wetting agent in the scouring stage to about 0.5 g/L to 2 g/L.
 22. A yarn dyed by the method of claim
 16. 23. A fabric, comprising: a plurality of the yarns of claim 22 woven together in the warp and weft directions.
 24. A garment comprising: the fabric of claim 23 sewn together with one or more other fabrics into a garment. 